THz-induced Kerr effect in polar liquids

We investigate the THz-field induced orientation of molecules in the liquid state by means of the Kerr effect. In contrast to an optical or near-infrared excitation, THz photons have frequencies below the intramolecular vibrations and therefore leave the internal structure of the molecule mostly unaffected. We find experimental evidence for a THz-induced optical birefringence, which provides evidence for molecular orientation. Experimental data on anethole and water reveal the potential application for molecular re-orientation during ultrafast chemical reactions.